Percussion drilling utilizing pellet rock drill bit



April 19, 1955 F. G. BOUCHER PERCUSSION DRILLING UTILIZING PELLET ROCK DRILL BIT Filed May 15, 1953 1'2 E ouher sfI-VQOGOL 0. Clbbpzrzegs Dram United States Patent PERCUSSION DRILLING UTILIZING PELLET ROCK DRILL BIT Frank G. Boucher, Tulsa, Okla., assignor to Esso Research and Engineering Company, a corporation of Delaware Application May 15, 1953, Serial No. 355,390

4 Claims. (Cl. 255-63) The present invention is concerned with an improved method and apparatus for the drilling of bore holes into the earths substrata. The invention is more particularly concerned with an improved method for the drilling of petroleum wells. In accordance with the present invention a novel procedure and improved drill bit is utilized to secure the circulation and retention of solid pellets in a bore hole so as to forc'ibly impinge the pellets on a percussion element or head adjacent the bottom of the hole for the purpose of deepening the hole. The impact of the pellets serve 'to provide percussion forces, thereby pulverizing the formation being penetrated. The cuttings are removed to the surface by the circulation of drilling fluid. Circulation and maintenance of the pellets in contact with the percussion head in the bottom of the hole is secured by an improved bit assembly which will be hereinafter described in detail.

In the art, it is felt that rotary drilling procedures are of the most practical value. Nevertheless, it is also appreciated that a need exists for improved drilling techniques and apparatus. The present invention is directed toward this objective; that is, of providing an improved drilling method. This objective is obtained by recourse to a radical innovation in drilling concepts. In order to appreciate the nature and advantages of this invention, it is useful to consider certain limitations of the presently employed rotary drilling operations.

In general, rotary drilling procedures employ a drill bit which is fixed to the lower end of a string of pipe designated as a drill string. Equipment is provided at the surface of the earth to progressively lower the drill string into the earth as the drill string is rotated by a prime mover. Drilling depends upon the direct action of the drill, forced against the bottom of the bore hole by the weight of the drill string. During rotary drilling, pumping facilities are required to circulate a fluid through the drill stem and bore hole which is called a drilling mud. This drilling mud is generally a high density liquid of a nature to lubricate the drill bit, to maintain a high hydrostatic pressure in the bore hole, to remove cuttings from the bore hole, and to perform other functions.

Rotary drilling procedures of this general nature are characterized by certain limitations which in large part account for the considerable expense involved in drilling. One difliculty for example, concerns the necessary replacement or reconditioning of the drill bit employed. As the drill bit becomes worn, it is necessary to remove the entire drill string from the earth, section by section. When the drill bit has then been replaced, the reverse procedure is necessary and the drill string is once more lowered into the earth, section by section, to bring the drill bit to its cutting horizon. Again, for example, to secure practical rates of drilling, substantial weight must be placed on the drill bit necessitating strong, heavy construction of the drill string, including particularly designed drill collars. Complicated, expensive derricks, including suitable rotary equipment are necessitated at the surface of the earth. These and other inherent characteristics of rotary drilling account for the expense of drilling by this procedure and in turn create the need for an improved drilling procedure.

It has also been suggested that the drilling procedure be improved by the impinging of hardened dense pellets on the bottom of a bore hole, propelled by high velocity fluid jet. The action of these pellets, carried by the high velocity jet is somewhat similar to that of sand blasting. While there is some doubt as to the actual mechanism of this drilling procedure, it appears probable that the action is primarily that of surface pulverization caused by the forceful and multitudinous impingement of the solid pellets against the earth formation encountered.

While this procedure is very effective and holds future commercial promise, one problem encountered is the replacement and the retention of the pellets in the bottom of the bore hole. This is due to the fact that the velocity of the upflowing drilling fluid tends to carry the pellets upwardly and out of the region where they can be elfectively recirculated through the jet. While this difficulty could be overcome to some extent by lowering the velocity, this is not practicaL due to the fact that it is desirable to recirculate a predetermined quantity of drilling mud per unit of time. Since the well bore has a fixed crosssectional area, it is obvious that there exists a minimu velocity that can be tolerated.

The process and apparatus of the present invention may be fully understood by reference to the drawings illustrating embodiments of the same.

Figure 1 illustrates the drill bit assembly of the present invention disposed down a bore hole.

Figure 2 is entirely similar to Figure 1 except that an inner cylindrical element is concentrically disposed within the drill bit assembly body in order to secure a more positive circulation of the pellets.

Referring specifically to Figure 1, the drill bit assembly is shown attached to the lower end of a drill string 10 disposed at the bottom of a well bore 11. The drill bit assembTy is attached to the lower end of the drill string 10 by threaded or equivalent means. The drill bit assembly comprises a cylindrical body element 3 having at its upper end a restricted nozzle 5 communicating with the inside of the drill string. The lower end of the drill bit body 3 comprises a heavy percussion or plate element 2. The percussion element 2 is characterized by having a serrated or toothed lower face 1. Cylindrical body element 3 is also characterized by having outlet ports 7 at the top shoulders thereof. The percussion or head element 2 is alsso characterized by containing a plurality of ports or ets In operation, drilling fluid is pumped down within the drill string 10. This fluid passes from the drill string through the restricted nozzle 5 and picks up in the fluid stream pellet elements 4. These pellets are hard, metallic alloys, as for example, various ferrous alloys. The size of the pellets may vary from about inch to 1 inch and larger in diameter. These pellets impinge upon the percussion element 2 at a relatively high velocity and then rebound outwardly and flow upwardly along the inner side of the cylindrical body element. Approximately 50-75% and more of the drilling fluid pumped down the drill stem passes through the port elements 6. This drillmg mud picks up the cuttings and passes upwardly to the surface in the area between the outer surface of cylindrical body element 3 and the wall of the well bore. The remaining drilling fluid passes upwardly through ports 7. The upfiowing pellets are repicked up by the downflowing stream at nozzle 5 and again flow downwardly and impinge on the percussion element.

Referring specifically to Figure 2, the construction is identical as that described with respect to Figure 1 except that an inner open-ended cylindrical conduit element 8 is concentrically disposed within the body element 3. In operation, the pellets 4 flow downwardly through conduit element 8, impinge on the head element 2, rebound and flow upwardly in the area between the inner wall of the body element and the outer surface of the cylindrical element.

What is claimed is:

1. Improved drill bit assembly which comprises a cylindrical body element adapted to be attached at its upper end to the lower end of a drill string, said cylindrical body element being characterized by having a restricted passageway at its upper end communicating with the inside of said drill string, said body being characterized by containing a plurality of ports at its upper end communicating with the area without said drill stem, said body being further characterized by having a lower heavy percussion impact base, said base being characterized by containing a plurality of openings communicating with the inside of said body element and the area below said body element, said passageway said spheres flow downwardly through and a plurality of metallic spheres contained within said said cylindrical element and upwardly in the area between body element. said body element and said cylindrical element.

2. Apparatus as defined by claim 1 wherein the lower surface of said percusfsiion egement is serrfilted. h l 5 References Cited in the file of this patent 3. Apparatus as de ned y claim 1 w erein t e ower surface of said percussion element is toothed. UNITED STATES PATENTS 4. Apparatus as defined by claim 1 wherein an open- 51,230 Smith et a1 Nov. 28, 1865 ended cylindrical element is concentrically disposed within 2,072,627 Zublin Mar. 2, 1937 said body element, whereby as fluid is pumped through 10 2,233,260 Hawthorne Feb. 25, 1941 

